Morphological, histochemical and morphometric study of the myotomal muscletissue of the pacu (Piaractus mesopotamicus Holmberg 1887: Serrasalminae, Characidae, Teleostei)
V. Dal Pai et al., Morphological, histochemical and morphometric study of the myotomal muscletissue of the pacu (Piaractus mesopotamicus Holmberg 1887: Serrasalminae, Characidae, Teleostei), ANAT HISTOL, 29(5), 2000, pp. 283-289
Histochemical, ultrastructural and morphometric methods were used to study
growth patterns of red, pink and white muscle fibres and their relation to
body weight and total length in the fast-growing freshwater fish Piaractus
mesopotamicus Holmberg. The correlations amongst body weight, body length a
nd diameter of red, pink and white fibres were low. From 10-15 to 40-50 cm,
body weight increased 102.7 times, while the diameter of each type of fibr
o increased by factors of 0.94, 0.74 and 0.70, respectively. Muscle fibres
revealed different morphological and histochemical stages of maturation. Th
e frequencies of < 20 <mu>m fibres of red, pink and white muscle tissue in
the youngest and oldest classes were 64.5 and 11.0, 38.2 and 7.7 and 24.0 a
nd 1.4%, respectively. In 30-40 cm fish, the frequency of < 20 <mu>m fibres
in the red and pink tissue was 24.5 and 25.5%, while in the white tissue i
t was 11.5%. During sexual maturity (40-50 cm), the recruitment of < 20 pm
fibres in white muscle was 1.4%. Muscle fibres of this species showed conti
nuous growth by both hyperplastic and hypertrophic mechanisms, and hyperpla
sia was particularly active in the juvenile phase.